Samuel C. Hughes

Intravenous Remifentanil Placental Transfer, Maternal and Neonatal Effects

Background Remifentanil has not been studied in obstetric patients. This study evaluates the placental transfer of remifentanil and the neonatal effects when administered as an intravenous infusion. Methods Nineteen parturients underwent nonemergent cesarean section with epidural anesthesia and received 0.1 [micro sign]g [middle dot] kg‐1 [middle dot] min‐1 remifentanil intravenously, which was continued until skin closure. Maternal arterial (MA), umbilical arterial (UA), and umbilical venous (UV) blood samples were obtained at delivery for analysis of drug concentrations of remifentanil, its metabolite, and blood gases. Maternal vital signs were monitored continuously, and pain and sedation levels were assessed intermittently. Apgar scores were obtained at 1, 5, 10, and 20 min, and Neonatal and Adaptive Capacity Scores were noted 30 and 60 min after delivery. Parturients and newborns were observed for at least 24 h after surgery for side effects. Results The means and SDs of UV:MA and UA:UV ratios for remifentanil were 0.88 +/‐ 0.78 and 0.29 +/‐ 0.07, respectively. Mean clearance was 93 ml [middle dot] min‐1 [middle dot] kg‐1. The mean UV:MA and UA:MV ratios for remifentanil acid were 0.56 +/‐ 0.29 and 1.23 +/‐ 0.89, respectively. The mean MA (remifentanil acid):MA (remifentanil) ratio was 2.92 +/‐ 3.65. There were no adverse effects on the neonates, but there was a sedative effect and respiratory depressant effect on the mothers. Conclusions Remifentanil crosses the placenta but appears to be rapidly metabolized, redistributed, or both. Maternal sedation and respiratory changes occur, but without adverse neonatal or maternal effects.

A new neurologic and adaptive capacity scoring system for evaluating obstetric medications in full-term newborns.

A variety of examinations are currently available for evaluating the neurobehavior of the newborn. These exams are often difficult and time-consuming to perform, require extensive training of the examiners, and produce results that may be difficult to interpret. The authors describe a new Neurologic and Adaptive Capacity Score (NACS) for full-term neonates and compare it with the Scanlon Early Neonatal Neurobehavioral Scale (ENNS), the most widely used test for evaluating effects of obstetric medication on the neonate. The NACS was designed as a screening test to detect central nervous system depression from drugs and also to differentiate these effects from those found after birth trauma and perinatal asphyxia. The NACS is based on 20 criteria, each of which is given a score of 0, 1, or 2. These criteria assess five general areas: 1) adaptive capacity; 2) passive tone; 3) active tone; 4) primary reflexes; and 5) alertness, crying, and motor activity (general observations). In contrast to the ENNS, the NACS places more emphasis on motor tone, avoids the use of noxious stimuli (pinprick, repeated Moro examinations), takes half the time to perform, and provides for any given baby a single number that immediately identifies a depressed or vigorous neonate.

Practice guidelines for the prevention, detection, and management of respiratory depression associated with neuraxial opioid administration.

PRACTICE guidelines are systematically developed recommendations that assist the practitioner and patient in making decisions about health care. These recommendations may be adopted, modified, or rejected according to clinical needs and constraints, and are not intended to replace local institutional policies. In addition, practice guidelines developed by the American Society of Anesthesiologists (ASA) are not intended as standards or absolute requirements, and their use cannot guarantee any specific outcome. Practice guidelines are subject to revision as warranted by the evolution of medical knowledge, technology, and practice. They provide basic recommendations that are supported by a synthesis and analysis of the current literature, expert and practitioner opinion, open forum commentary, and clinical feasibility data. This document updates the “Practice Guidelines for the Prevention, Detection and Management of Respiratory Depression Associated with Neuraxial Opioid Administration” adopted by ASA in 2007, and includes new survey data and recommendations pertaining to monitoring for respiratory depression. Methodology

Parturients Infected with Human Immunodeficiency Virus and Regional Anesthesia Clinical and Immunologic Response

Background It is estimated that 1.5 million Americans are infected with the human immunodeficiency virus (HIV‐1), and the consequences of HIV infection are a leading cause of death in women aged 15–44 yr. Thus, HIV‐1 disease, or acquired immunodeficiency syndrome, occurs with increasing frequency in the parturient, and there is little information concerning the risks of regional anesthesia. Fear of spreading infection to the central nervous system or adverse neurologic sequelae have led some clinicians to advise against regional anesthesia. Thus, this study was undertaken to evaluate the possible problems or risks associated with regional anesthesia in parturients infected with HIV‐1 and to determine whether anesthesia affected the clinical course of the disease. Methods The clinical course and immunologic function of 30 parturients infected with HIV‐1 were evaluated prospectively. Extensive medical and laboratory evaluation before delivery and 4–6 months postpartum was undertaken. Medical problems related to HIV‐1 disease and use of antiviral drugs also were monitored. The anesthetic management was dictated by the clinical situation and the patients wishes with careful postpartum follow‐up to evaluate possible neurologic changes or infection. Results Regional anesthesia was administered in 18 parturients, and 12 received small doses of opioids or no analgesia. There were no changes in the immunologic parameters studied (CD4 sup + p24, beta sub 2 microglobulins), and HIV‐1 disease remained stable in the peripartum period. There were no infections, complications, or neurologic changes in the peripartum period. Sixty‐eight percent of the infants were HIV‐l‐negative and, in 21% of infants, the HIV‐1 status was indeterminate (probably negative). Conclusions This prospective study of parturients infected with HIV‐1 demonstrated that regional anesthesia can be performed without adverse sequelae. There were no neurologic or infectious complications related to the obstetric or anesthetic course. The immune function of the parturient was stable in the peripartum period. Although the number of patients studied was small, with careful medical evaluation, regional anesthesia is an acceptable choice in the parturient infected with HIV‐1.

Epidural Morphine for the Relief of Postoperative Pain after Cesarean Delivery

To determine the safety, efficacy, and dose response of epidurally administered morphine for analgesia after cesarean delivery, 40 healthy women who underwent cesarean delivery with epidural anesthesia were randomly assigned to receive one of four regimens for relief of postoperative pain: intramuscular administration of morphine, 7.5 mg (N = 10); or epidural administration of morphine, 2 mg (N = 10), 5 mg (N = 10), or 7.5 mg (N = 10). Evaluations were made of intensity and relief of pain, time to administration of additional analgesic medications, changes in vital signs and blood-gas tensions, and adverse effects. Intramuscular administration of 7.5 mg of morphine effectively relieved pain for only a short time. When morphine was administered epidurally, 2 mg proved ineffective whereas both 5 mg and 7.5 mg provided substantial pain relief for approximately 24 h. There were no significant changes in vital signs or blood-gas tensions. Side effects included pruritus and nausea, which occurred frequently but were usually mild and easily treated. We concluded that either 5 mg or 7.5 mg of morphine epidurally administered was effective and safe in providing prolonged analgesia after cesarean delivery.

Neonatal neurobehavioral effects of inhalation analgesia for vaginal delivery.

The authors studied the neonatal neurobehavioral effects of nitrous oxide: oxygen and enflurane: oxygen inhalation analgesia for vaginal delivery. Parturients were assigned randomly to receive no inhalation agent (Group 1, n = 21); enflurane, 0.3 to 0.8 per cent, and oxygen (Group 2, n = 22); or nitrous oxide, 30 to 50 per cent, and oxygen (Group 3, n = 18). Infants were tested at 15 min, 2 h, and 24 h of age using the Neurologic and Adaptive Capacity Score (NACS); and at 2 and 24 h using the Early Neonatal Neurobehavioral Scale (ENNS). No significant differences in neurobehavioral status occurred. For all groups, scores tended to be lowest at two hours of age. We conclude that neither enflurane nor nitrous oxide analgesia adversely affects neonatal neurobehavioral status at 15 min, 2 h, or 24 h of age.

Enflurane analgesia in obstetrics.

: The effects of enflurane analgesia (approximately 0.5%) were studied in 55 patients during the second stage of normal vaginal delivery and were compared with effects of nitrous oxide (approximately 40%) in 50 similar patients. The enflurane and oxygen mixture was rated satisfactory by 89% of the mothers and 80% of the anesthesiologists. These ratings did not differ significantly from those for nitrous oxide. Obstetricians, however, rated the enflurane and oxygen mixture superior. The newborns of mothers receiving both agents wee vigorous and comparable when assessed by Apgar scores and cord blood gas tensions. The estimate of blood loss was similar in both groups. Serum inorganic fluoride concentrations in the mother after anesthesia were not significantly increased from preanesthetic levels with either agent. There was no biochemical evidence of renal toxicity. In neonates of mothers given enflurane, the mean umbilical cord concentration of serum inorganic fluoride ions was 2.4 +/- 0.2 micromoles/L, a value well below that associated with nephrotoxicity.

Hydralazine Does Not Restore Uterine Blood Flow during Cocaine-induced Hypertension in the Pregnant Ewe

Cocaine abuse is widespread, and its use by the parturient has potential significant adverse effects in both the mother and the newborn. This study was undertaken in gravid ewes to determine the effects of treatment of cocaine-induced hypertension with hydralazine (Apresoline) on the maternal and fetal cardiovascular systems, catecholamine response, blood gas and acid-base status, and uterine blood flow (UBF). Twenty-one experiments were performed in 15 chronically instrumented ewes near term gestation. After a 30-min control period, cocaine was given intravenously to all ewes for 55 min to induce and maintain increased maternal mean arterial pressure (MMAP) and reduced UBF. The sheep were randomly assigned to receive either cocaine alone (n = 11, control group) or hydralazine (n = 10, treatment group), starting 15 min after the cocaine administration. Both drugs were discontinued 55 min after the start of the cocaine administration, followed by a 35-min recovery period. In the control group, cocaine administration resulted in a 31 +/- 13% (SD) increase in MMAP (P less than 0.05) and a 26 +/- 21% reduction in UBF (P less than 0.05). In the treatment group, the initial cocaine administration resulted in a similar increase in MMAP and decrease in UBF. Hydralazine therapy restored MMAP toward baseline after 20 min of administration, but UBF remained reduced (37 +/- 17%) throughout therapy (P less than 0.05) and recovery (18 +/- 13%) (P less than 0.05). The maternal heart rate increased maximally by 121 +/- 33% (P less than 0.05) after the administration of hydralazine, compared with a 14 +/- 21% increase (P less than 0.05) in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Maternal anesthesia and the stressed fetus: effects of isoflurane on the asphyxiated fetal lamb

The effects of maternal isoflurane-oxygen anesthesia (isoflurane, 1% inspired) were measured in eight pregnant ewes and their asphyxiated singleton fetuses. Stable fetal asphyxia, indicated by a stable fetal arterial pH of 7.1-7.2 units, was produced by maternal uterine artery occlusion. Maternal and fetal heart rates and blood pressures; maternal uterine artery flow; maternal arterial, fetal arterial, and sagittal sinus pH; and blood gas tensions were determined during an awake control period, during fetal asphyxia alone, and during fetal asphyxia plus isoflurane-oxygen. Measurements of representative fetal whole organ blood flows, cardiac output, and cerebral oxygen consumption were also made during each of the three experimental periods. During asphyxia alone regional and total brain, heart, and adrenal flows increased above control while flow to the spleen and carcass decreased. Similar responses were seen during asphyxia plus isoflurane-oxygen. Fetal arterial and sagittal sinus pH, base excess, po2, and oxygen saturation decreased, and hydrogen ion concentrations and pco2 increased during asphyxia alone and asphyxia plus isoflurane-oxygen. Cerebral oxygen consumption decreased significantly from control during asphyxia plus isoflurane-oxygen, whereas no significant changes occurred in cerebral oxygen delivery. These results support the conclusions that in the asphyxiated fetus: 1) acidosis is increased; 2) cardiac output is redistributed to vital organs; and 3) the balance of cerebral oxygen supply-to-demand is maintained during maternal isoflurane-oxygen anesthesia.

Hemodynamic Effects of Prostaglandin E2

Prostaglandin (PG)E 2 has been used in obstetrics for several years as a mid-trimester abortifacient. The known side effects of PGE 2 include an increase in heart rate, pyrexia in 40% of patients, and tachypnea, which are well known to obstetricians. Although the central and peripheral effects of PGE 2 have been studied in animals, the potentially significant hemodynamic changes detectable by monitoring with a pulmonary-artery catheter are minimally explored in humans. We report our observations in a patient with the diagnosis of preeclampsia monitored with a pulmonary-artery catheter during treatment with PGE 2